Motor control system



w. H. sMrrH uo'ron CONTROL SYSTEM Jan. 19, 1932.

Filed Sept. 24'. 19.26

2 Sheets-Shet INVENTOR Walter/ Smith WITNESSES:

TToRNEY Jan. 19, 1932. w. H. SMITH 1,841,555

MOTOR CONTROL SYSTEM Filed Sept. 24,-1926 2 Sheets-Sheet 2 WITNESS INVENTOR 0 1 Q Walter H. Smith ATTORNEY can not be maintained to operation and nil Patented Jan. 19, 1932 unrrao sT'ATEs PATENT I OFFICE WALTER H. SMITH, OFWILKINSBURG, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA MOTOR CONTROL SYSTEM Application filed September 24, 1926. Serial No. 137,509.

This invention relates generally to improven'ients in motor-control systems, and more particularlyto motor-control systems in which the connectionsare changed during the operation of the motor.

In the operation of motors with repulsion connections, there has been considerable arcing upon the application of power to the motors when rotated mechanically at or above a. predetermined speed. This results in injury to the commutator, and necessitates the continual re-conditioning of the motor, which greatly increases the cost of operation. F urther, the maximum efliciency of the motor over any considerable period.

The object of this invention, generally stated, is the provision of a motor-control system which shall be simple and efficient in readily and economically manufactured and installed.

A morespecitic object of the invention is to provide an improved motor-control system for the starting and accelerating of a motor with repulsion connections, and the operation of the motor, when it reaches a predetermined speed, with doubly-fed connections.

A fin't-hcr object of the invention is to provide for aut miatically changing the-repulsion connections of a motor to doubly-fed connections when the motor rotates at a predetermined speed. i

It is also an object of-the invention to provide for the establishment of doubly-fed connections for operating the motor when power app-lied to it and it is rotating at, or above, a predetermined speed.

Other objects of the invention will, in part,

be obvious and, in part, appear hereinafter.

The invention is disclosed in the embodiment thereof shown in the accompanying drawings and comprises the features of construction, combination ofelements and arran gement of parts which will be exemplified in. the construction hereinafter set forth and the scope of the application'of which will be indicated in the claims. 7

For a fuller understanding of the nature and objects of the invention, reference should e had to the following detailed description taken in conjunction with the accompanying drawings; in which Fig. 1 is a diagrammatic view of the preferred main circuits for supplying the traction motors of a railway vehicle from a power source. I

Fig; 1-A is a diagrammatic view of the auxiliary or control circuits for governing the establishment of the motor circuits in accordance with this invention.

Fig. 1B' is a diagrammatic view of an air-engine of a well-known type that may be utilized for actuating the sequence-drum of he control circuit shown in Fig. 1A.

Fig. 2 is a sequence chart showing the order in which the switches are closed.

Fig. 3 is a diagrammatic View of the motor circuits for a single motor, showingthe repulsion and doubly-fed connections for the field windings.

Referring now to the drawings, in Fig. 1 is illustrated the manner in which a plurality of motors and 11 may be connected across the secondary winding 12 of a transformer 13. which, in this particular case, is the source of supply-of electrical energy. As shown, the primary winding 14 of the transformer 13 is fed from an overhead trolley conductor 15 through a pantagraph 16.

Since one object of this invention is to start and accelerate the motor as arepulsion machine and to operate it, after it has gained a predetermined speed, as a doubly-fed machine, a plurality of switches 17 to 23, inclusive, are provided for making the desired repulsion and doubly-fed connections between the motors and the source of supply at different times.

' The motors l0 and 11 may be of any wellknown single-phase commutator type and are provided with main field windings 24 and 25 and auxiliary field windings 26 and 27. -As shown, the field windings 24 .to 27, inclusive, are connected in series relation with the armatures of the motors but it is to be understood that any other suitable arrangement of the field windings and armatures may be adopted.

In order to organize the control circuits shown in Fig. l, a manually operated coniii troller of any well-known type is provided. As shown in Fig. l-fli, the controller 28 com prises a, plurality oil contact segments to 32, inclusive, which are disaosed for movement into engagement with a plurality of contact lingers.

The contact lingers are arranged in two groups 33 to 36, inclusive, and 37 to 40, inclusive. The ccmtict fingers to 3G, inclusive, are disposed for engagement by the con tact segments 29 to 30, according as the controller is operated in the forward or in the reverse direction. lVhen the controller is moved in the forward direction, the contact segment 31 is withdrawn from the contact fingers 39 and l0, while the contact segment 32 is drawn into engagement with the contact finger 38. Vixen the controller is moved in the reverse direction, to reverse the rotation of the motors, a projection -A that is provided on the contact segment 2:30, is moved into engagement with the contact finger 37.

Associated with the controller 28 is an auxiliary drum 4-1, which may be actuated to a forward or a reverse position by means of coils 42 and 43. As shown, the coils 4:2 and 4-3 a re connected to the contact fingers 37 and 38 by conductors 44 and 45, respectively. These coils 4:2 and 43 are also connected to a negative conductor l7 through conductor l8.

In this construction, the auxiliary drum ll is provided with contact segments 49 and 50. As shown, these contact segments are disposed to engage two groups of contact fingers 51 to 53, inclusive, and l to 56, inclusive. \Vhen the auxiliary drum is moved to its forward position, the contact segn'ient 49 engages the contact fingers 51 and 52, while the contact segment engages the contact fingers and 55.

The cont ct linger is connected, by means of a conductor 5?, through an overload relay switch 58 to the actuating coil oil switch 22. Further. the contactlingcr 5i connectcd, by means of a conductor 60, to the conductor -l5 so that, when the controller 28 is set in its forward position, current may [low to the actuating coil ot the switch 22 from the battery source (ll which connected to the cont; ct linger by a conductor 62.

Since the operation of the control circuit is similar for hoth forward and reverse operations, it is thought that it will he sullicient to trace the circuits t at are established when the controller actuated to its for ward position. it is, therefor, considered unnc essary to explain and ai iply numerals to the conductors leading from the contact fingers of the auxiliary drum not already described, since they will take no part in the operation of the control circuits to be explained hcrciinri'ter, and such a procedure would 0. 1 add to the complexity of the drawings.

The actuating coil of switch 22 is also con nected by a conductor to interlock 4L6. Two other interlocks G4: and (55 are provided in conjunction with the switch 2 and are disposed to engage two groups of contact fingers 66 to 68, inclusive, and (if) to 71, inclusive, respectively, when the switch is closed.

Assume now that the controller 28 is actuated to its third position in the forward direction, current then flows trom the l'iattery 61 through conductor 62, contact linger 34, contact segments 30, a and 232, contact linger 38, conductor 4:5. actuating coil e3, interlock L6 and conductm' to the grounded conductor ll. In this manner, the auxiliary drum 4l-1 is actuated to its forward position.

hen the contact segment all) is moved into engagement with the contact fingers 51 and the actuating circuit of the switcn 22 is established. Current now flows from the energized conductor 41:) through conductor 60, contact fingers 5i and 52, bridged hy the contact segment L9, the overload relay switch 59, conductor 57, the actuating coil of the switch 22, conductor 63, interlock l6, and conductor 4L8 the grounded conductor 47. Accord ingly, the switch is closed and the interlocks (i l and 65, carried by it, are moved into engagement with the groups ot contact fingers 66 to 68, inclusive, and 69 to Tl, inclusive.

The actuation of the interlocks (rt and (35 into ci'igagcment with their respective contact lingers closes the actuating circuit for the switcl'i 19. Current now flows from the hattcry 61 through conductor (32, contact lingers 34 and 33, bridged by the contact scgmei'it 3i). conductor 72. contact iuger 69, interlock (55, contact finger 71, onductor 73, contact tiners T l and 75, which are bridged by the contact segment 76 of the sequence drum 7 conductor 79, the actuating coil of the switch '19. conductor 81,. contact fingers and '191, bridged by interlock 192 and conductor 82 to the grounded conductor 47. Switch 19 is now closed, as shown in Fig. 2, and the two interlocks R3 and 84. carried by it are operated. As shown, the interlock 83 is moved into engagement with the contact fingers S5 to 87, inclusive. while the interlock Pr-l is moved out of engagement with the contact lingers 88 and 89.

As will be observed, the motor circuit is now closed, the motors l0 and 11 being connected across a portion of the secondary winding 12 of the transformer The motor circuit may he traced as follows; from the transtorniicr secondary winding); 12, through switch motors l0 and 11 in scrim; relation, main field windings 2- l and conductor 90, the actuating coil 91 ot a relay 92, conductor 93, auxiliary field windings 26 and 27, a portion of the preventive coil 94:, condnctor 95, and switch 19 to the l1211]%;'f)11l1(%!. This causes a considerable current to How in the actuating coil 91 of the relay, but it is not sufficient to raise the contactor-96.

The relay 92 will be set forth in detail in my copending application, Serial No. 140,534, but in order that the operation of the control circuits may be more clearly understood, certain features of its construction will now be explained. As shown, the relay comprises a core 97, from which depends a shaft 98. In order to utilize the relay for controlling c1r-.

cuits, a contactor 96 is mounted in a predetermined position on the shaft and is disposed to engage contact members 100 and 101.

The actuating coil 91, already referred to, is associated with the core 97 for actuating the contactor 96. In order to restrict the operation of the'relay through the energization of the actuating coil 91, a weight 102 is slidably mounted on the shaft 98. 'When in its lowermost position, the weight 102 is carried by the shaft 98 and is located only a short distance above the horizontal arm of a bell crank 103.

The lower arm of the bell crank is adapted to serve as an armature and is disposed in alinement with a coil 104. Accordingly, when the coil 104 is energized, the bell crank may be oscillated counter-clockwise to lift the weight 102 to cooperatewith the actuating coil 91 in actuating the contactor 96.

In some cases, an auxiliary coil 105, which may be connected to any suitable source of supply, may be provided for retarding the operation of the bell crank. However, since the use of a coil, such as 105, does not change the operation of the control circuit, further description of it and its energization is considered unnecessary.

Upon the closure of the switch 19, another circuit is established which serves to energize the actuating coil of the switch 18. This circuit may be traced as follows: from battery 61, through conductor 62, contact fingers 34 and 33, bridged by the contact segment30, conductor 72, contact fingers 69 and 71, bridged by the contact segment 65, conductor 73, contact fingers 74 and 107, bridged by the contact segment 108 of the sequence drum 78, conductor 109, actuating coil of the switch 18, conductor 129, contact fingers 111 and 112, bridged by interlock 113 of the switch 17, conductor 110, contact fingers 87 and 85, bridged by the interlock 83, and conductor 114 to the grounded conductor 47.

Therefore, the switch 18 is closed and the interlocks 115 and 116 mounted thereon are actuated to their out and in positions, respectively. As will be observed by reference to the drawings, the interlock 115is disposed to engage the contact fingers 117 and 118, when the switch is open, and the interlock 116 to engage the contact fingers 119 and 120 when the switch is closed;

Closure of the switch 18 .causes an increase in the voltage applied to the motor circuit and, therefore, an increase in the current energizing coil 91. However, in designing the members 97, 96 and the weight 102, they are made of sufficient weight to prevent operation of the relay by the which will flow in the motor circuit when p the switches 18, 19 and 22 are closed and the motor is rotating. Upon the closure of the switch 18, an-

other circuit is established which servesto energize the a1r-eng1ne 122,

shown in Fig. 1B. As will be observed, the air-engine 122 is of a well-knowntype such as shown in Patent 1,229,543 and is provided with off and on valvesactuating coils 123 and 124, respectively; As in the usual construction, when both of the valve=actuating coils are energized, the engine operates in one direction, but, when both are de-ene'rgized, it moves in the other direction. If the on coil only is energized, the air-engine may be stopped in any desired position.

The'air-engine is provided for operating the sequence drum 78. As shown schematically in the Figs. l-A and 1-B, the air engine is connected to the sequence. drum by means of a'shaft 125..

The circuits established upon the closure of the switch 18, which cooperate with the actuation of the 'air-engine, may be traced as follows: from the energized conductor 72, through contact fingers 69 and 70, bridged by the interlock 65 of switch 22, conductor 121, the on coil 124 of the air-engine, conductor 126, contact fingers 68 and 67, bridged by the interlock 64, and conductor 127 to the grounded conductor 47. The other coil 123 of the air-engine is connected in the circuit which extends from the energized conductor 7 2, through contact fingers 69 and 70, bridged by the interlock 65, conductor 121, conductor 128, contact fingers 119 and 120, bridged by the interlock 116, conductor 169, contact fingers 130 and 131, bridged by the contact segment 132, conductor 133, off coil 123 of the air-engine, conductor 126, contact fingers 68 and 67, bridged by the interlock 64, and conductor 127 to the grounded conductor 47 Since both the valve-actuating coils 123 and 124 of the air-engine 122 are energized, it will immediately begin to move the sequence drum '78 forward, It will be observed that, when the sequence drum reaches its first position, the contact finger'130 is disengaged from the contact segment 132. Thus, coil 123 is deenergized while coil 124 remains energized,

and the air-engine is brought to rest.

At: the same tilnefthat the energizing circuits for the air-engine are established,- annormal current a other circuit is closed which serves to energize'the coil 104 of relay 92. 'This circuit also leads from the energizing conductor 72 through-contact fingers 69 and 70, bridged by the interlock 65, conductor 1 21, conductor 128, contact fingers 119 and 120, bridged by the interlock 116, conductor 169, contact fingers 130 and 134, bridged by the contact segment 132, conductor 135, coil 10%, conductor 13G, conductor 126, contact fingers 68 and 67, bridged by the interlock (i l, and conductor 127 to the grounded conductor 17. Upon the energization of the coil 10 1, the bell crank 103 rotated counter-clockwise, and the weight 102 is lifted.

As soon as the members 97 and 98 are relieved of the weight 102, they are actuated by the coil 91. Consequently, the contactor 96 is raised and the actuating coil of the switch 21 can not be energized therethrough when the contact segment 137 on the sequence drum is moved into engagement with the con tact lingers 138 and 139.

\Vh en the sequence drum 7 8 reaches its first position, the circuit for energizing the actuating coil of switch 23 is completed. Again we start with the energizing conductor 72 and continue through the contact fingers 69 and 71, bridged by the interlock 65, conductor '7 3, contact fingers 74 and 1410, which are bridged by the contact segment 76, conductor 141, contact fingers 1 12 and 143, bridged by interlock 14:4: on the switch 21, the actuating coil of the switch 23 and conductor 116 to the grounded conductor 17. The closure of the switch 23 increases the voltage applied to the coil 91 and raises the current to a value sul'iicient to effect the operation of the relay without the assistance of the relay coil 104.

The initial connections are now completed and the motors, which are connected across a section of the secondary winding of the transformer, operate as repulsion machines. As soon as the speed of the motor increases, the current flowing in the field windings is reduced to such a value that the coil 91 can not retain the contact member 96 in its raised position, and itis dropped to complete a circuit which serves to energize the actuating coils of the air-engine.

The switch 23 is provided with an interlock 117 that is disposed to engage contact lingers 11-8 and 1&9 when the switch is open. \Vhen the switch 23 is closed, the interlock 11-7 is moved out of engagement with the contact fingers 1 13 and 149.

The sequence drum remains in position 1 until the motors rotate at a sullicient speed to cut down the current flowing in the field windings 24; to 27, inclusive, and therefore, the current flowing in the actuating coil 91 of the relay 92. hen the energization of the coil 91 sulficiently decreased, it will permit the contactor 96 to drop into engagement with the contact members 100 and 101. This establishes a new energizing circuit for the ofi' VtllVQ-tICtHtttl'ilg}; coil 123 of the airengine 122.

The circuit thus established by means of the relay comprises the battery 61, conductor 62, contact lingers 3a and 35, bridged by the contact segment 30, conductor 150, contact fingers 151 and 152, bridged by the contact segment 150 of the sequence drum, conductor 15%, contact member 155, the upper arm of the bell crank 103 of relay 92, conductor 156, contact members 101 and 100, bridged by the contactor 96, conductor 157, contact fingers 153 and 131, bridged by the contact segment 132, conductor 133, the actuating coil 123, (mnductor 126, contact lingers (i8 and (57, bridged by the interlock ($4, and conductor 127 to the grounded conductor 17. T he energizing circuit of the on valveactuating coil 121 was not broken during the first step of movement of the sequence drum, and so the two valve-actuating coils are now energized and the sequence drum moves forward from position 1 toward position It will be nmed that, as the sequence drum progresses from position 1 to position 2, the contact linger 107 is disengaged from the contact segment 7 (5, thereby deenergizing the actuating coil of the switch 18. This action causes the interlock 115 to engage the contact lingers 117 and 113.

The contact finger 159 is engaged by the contact segment 76 when the drum 78 is moved from position 1 to position 2 and an energizing circuit for the switch 17 is closed. Current now 'llows from the energizing conductor 72 throu contact lingers 69 and 71, bridged by the interlock (35, conductor 73, contact lingers 7 1 and 159, bridged by the contact segment 76, coiuluctor 1G0, actuating coil of the switch 17, conductor 172, contact iiugers 1.17 and 113, bridged by the contact segment 115, and througu conductor 173 to the grounded conductor -17. 'lhereiiore, switch 17 is closed.

It will be noted that, as the sequence drum 78 moves from position 2 to position 3, the contact finger 1410 is diseng ged from the contact segment 76. Thus, the energizing circuit oi" the switch 23 opened and the interlock 117 is actuated to bridge contact lingers 1 18 and 1 1-9. 7

Further, as the sequence drum progresses from position 5 position 3, contact linger 138 is engaged by the contact segment 70. This closes a circuit leading "from the energized conductor 72 through contact lingers (i9 and 71, bridggged by the interlock 65, conductor 73, contact fingers 7 4; and 13S, bridged by the contact segment 7 (3, conductor 175, contact fingers 176 and 177, bridged by the interlock 17S. conductor 179, actuating coil oli switch 21, conducti'ir 131, contact lingers 119 and 1 1-3, bridg d by the nterlock 1 117, and conductor .182 to the grounded conductor 4-7. Consequently, when the above circuit is en ergized, the switch 21 closed, thereby b ringing about the establishment of: the doubly-ted notor connections.

The motors are now energized by two circuits. It will be seen that one circuit extends from the secondary winding 12 of the transformer, through switch 22, the armatures of motors and 11, main field windings 24 and 25, conductor 90, relay coil 91, conductor 93,

I auxiliary field windings 26 and 27, the preventive coil 94 and switches 17 and 19, to the transformer. The other circuit extends from the secondary winding 12, through switch22, the armatures of the motors 10 and 11, main field windings 24 and 25, to the secondary winding 12 through switch 21.

The movement of the sequence drum. from position 2 to position 3 is eii'ected by substantially the same circuit as brought about the movement from position 1 to position 2, with the exception that the conductor 183, instead of the conductor 150, is connected between the contact segments 15.3 and the battery 61, This circuit is established when the current flowing in the coil 91 is reduced by the counter-electromotive force developed in the motors as the speed increases, so as to permit the closure of the contact member 96.

The starting and accelerating of the motors with repulsion connections and the establishment of doubly-fed connections for the-normal starting of the motors fromrest, is as described above. However, when motors of this-type are used for operati'ng'vehicles, it is often desirable to cut off the power when the vehicle is coasting and the motors are beingdriven mechanically, so as to conserve energy. If occasion demands that the power he re-applied when the vehicle is still'coasting and the motors are rotatinga'ta predetermined speed, provision is made for re-establishing the doubly fed connections only,

. thereby to prevent arcing and injury'tothe commutator. V

Assume now that the vehlcle is movmg, and that the operator'has manipulated the controller to cut oil the supply of electricalenergy, which eiiects the de-energization of the valve-actuating coils 123 and 124, so that the air-engine 122 returns the sequence drum 78 to its oil position. Under such conditions, the switches 17 to 23, inclusive, are

- opened and the motors are completely disconnected from the transformer '13.,

If it becomes necessary, tore-apply power while the vehicle is still coastingfat a speed which, for this particular. apparatus, is about thirty miles per hour, anumber of circuits will be re-established when the .master controller 28 is thrown to its third position. 1 The actuating circuits for the switches22, 19 and 18 will be the same as those established for the initial starting and accelerating of the motor, with the repulsion connections described hereinbefore; In addition to these circuits, new circuits will be established for effecting the closure of theswitch 21 to immediately bring about the establishment of the doubly-fed connections.

lVhen the motors are being driven mechanically at a predetermined speed, an electromotive force is developed which, upon the re-application of power to the motors, prevents the building up of a current-in the motor circuit suflicient to effect the energization of the coil 91 to a value equal to that required to actuate the contactor 96. Consequently, the circuit through the relay, which serves to energize the actuating coil of the switch 21, is closed.

As will be readily understood from the description already'given, when the switches 18, 19 and 22 have been closed, circuits are established for the energization of the valveactuating coils 123 and 124. Accordingly, the air-engine will function to move the sequence drum7 8 forward. 1

As the sequence drum moves from its 011" posit-ion toward itsfirst position, a circuit is established from the energized conductor 72, through contact fingers 69 and 70, bridged by the interlock 65, conductor 121, contact fingers 174and 158, bridged by the contact member 132, conductor 157, contact fingers 100 to 101 bridged by contactor 96, conductor 185, contactfingers 138 and 139, bridged by the contact segment 137, conductor 17 5, contact fingers 176 and 177, bridged by theinterlock 178, conductor 179, actuating coil of the switch 21, conductor 181, contact fingers 149 and 148, bridged by the interlock 147, and conductor 182 to the grounded conductor 47. In this manner, the'switch 21 is closed to establish the doubly-fed connections' as the sequence drum moves. from its off position to'its first position.

' It will be notedthat, as the sequence drum moves from its off position to its first position, the contact fingers 138 and 139 are disengaged from the contact segment 137, thus interrupting the energizing circuit for the switch21. However, as described above, be-

fore the circuit traced for actuating switch 21 is broken, thecontactfinger 140 is engaged by the contact segment 76, and a holding circuit is established formaintaining the switch 21 closed. This circuit extends from the energized conductor 72, through contactlfingers 69 and 71, bridged by the interlock 65, conductor 73, contact fingers 74 and 140, bridged by'the contact segment 76, conductor 141,'contact fingers 142 and 186, bridged by V the interlock 144, conductor 179, actuating coil of switch'21, conductor 181, contact fin.- gers 149 and 148, bridged by the interlock 147, and conductor 182, to the grounded conduc tor 47 This holding circuit was made possible by the actuation of the interlock 144 into engagement withcontact fingers 185 and 186, which action was efiected switch 21.

by the closure of the 1 It will be noted that, when the master controller 28 was thrown to its on position, the circuit for energizing the coil 10% was established in the same manner that it was established during the initial starting of the motor from rest with repulsion motor connections. The energization of the coil 104 ettects the operation of the bell crank 103 to lift the weight 102. However, when the motors are mechanically rotated at a high speed, the electromotive force developed prevents the flow of sufficient current in the coil 91 to operate the relay contactor 96 even when relieved of the weight 102.

It will, therefore, be seen that, when the master controller 28 actuated, the switches 18, 19, 21 and 22 are closed to establish doubly-fed connections, if the motors are being rotated mechanically at a predetermined speed, but to establish repulsion connections it the motors are at rest.

Since numerous changes may be made in the above described construction and arrangement of parts and different embodiments of the invention may also be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

I claim my invention:

1. In a motor control system in combina tion, a source of power, a motor, manually operable control means for effecting the connection of the motor to the source of power, control means responsive to the operatioi'i of said manual control means for connecting the motor to the power source to start it as a repulsion motor and operate it as a doubly-ted motor, and a relay disposed to stand inactive when the motor is rotating above a pre( etcrmined speed to permit the establishment of doubly-fed motor connections, when the manually operable control means is actuated.

2. In a motor control system in combination, a power source, a motor, a plurality of switches for connecting the motor to the power source to operate it either as a repulsion motor or a doubly-fed motor, a sequence drum disposed for operation to control the switches provided for establishing the doubly-fed connections, said sequence drum being adapted to establish the doubly-fed connections in its first operating and other predetermined positions, means responsive to motor currents for preventing the sequence drum from establishing connections for operating the motor as a doublyded machine when in its first position it the motor is being started from rest, said preventive means being disposed to stand inactive when the motor is operating at a predeterminer speed thereby permitting the establishment oi the doubly'ted motor connections when the se quence drum is actuated to its first operating position to effect the connection of a mechanically driven motor to the power source.

In a motor control system in combination, a power source, a motor disposed to be connected to the power source, control means comprising manually operable means, a sequence drum, means for actuating the sequence drum and means responsive to the operation of the manual means and the sequence drum for connecting the motor to the power source to operate it as a repulsion motor or a doubly-ted motor, said sequence drum being disposed to establish doubly-ted motor connections when actuated to its first operating position and a relay responsive to motor currents disposed to prevent the establishment of doubly-fed connections for the motor when the motor is started lron'i rest and disposed to stand inactive when the motor is rotating at or above a predetermined speed, thereby to permit the establishment of doubly-fed connections by the use of said manually operable means.

4. In a motor control system in combination, a power source, a motor disposed to be connected to the power source, control means comprising manually operable means, a sequence drum, means for actuating the sequence drum and means responsive to the operation of the manual means and the se' quence drum for connecting the motor to the power source to operate it as a repulsion motor or a doubly-fed motor, said sequence drum being disposed to establish doubly-fed motor connections when actuated to its first operating position and a relay responsive to motor currents disposed to prevent the establishment of doubly-l ed connections for the motor when the motor is started from rest, said relay being disposed to stand inactive if the motor is operating at a predetermined speed, thereby to permit the establishment of the doubly-fed connections by the operation of the manually actuated control means.

5. In a motor-control system, in combination, a power source, a motor, a controller for governing the operations of the motor, means cooperative with the controller to establish repulsion connections to start the motor, said means being disposed to stand. inactive when the controller is actuated to establish motor connections and the motor is rotating at a predetermined speed.

6. In a motor-control system, in combination, a source of power, a motor, a controller for effecting the connection of the motor to the source of power, means disposed to cooperate with the controller to establish doubly-fed motor connections when the cow troller is actuated from its oil position and the motor is rotating above a predetermined speed, and a relay disposed to cooperate with the controller to establish repulsion motor connections when the controller is actuated from its off position and the motor is at rest, said relay being disposed to stand inactive when the motor is rotating at a predetermined speed.

7. In a motor-control system, in combination, a mo tor, a source of power for the motor, a controller for connecting the motor to the source of power, control means disposed to respond to the operation of the controller to establish repulsion connections for starting and accelerating the motor, and a relay cooperative to establish doubly-fed connections when the motor has reached a predetermined speed, said relay being disposed to stand inactive when the motor rotates at said predetermined speed and the controller is actuated to interrupt and reestablish connections to the source of power.

In testimony whereof, I have hereunto subscribed my name this 8th day of September,

WALTER H. SMITH. 

